My reading of this, in context with the previous bit, has a subtle difference:
With contact tracing, you get contact data from person 2 and you keep that data. Then you get contact data from person 3, and you keep that data too, and by the time you get to person 4, you have fairly strong evidence that person 1 is an asymptomatic carrier and you can do that without quarantining anyone asymptomatic.
With exposure notification, you get contact data from person 2, and tell everyone they were in contact with, and then throw away that data. Then you get information from person 3 and you notify everyone they were in contact with, and then throw away that data too. As a researcher, even after person 8 you don't have any evidence that person 1 is an asymptomatic carrier (because you threw that evidence away at each step) and the best responsible asymptomatic people can do is assume they're asymptomatic carriers whenever they receive an exposure notification--they'll never actually know.
The key differences (which I italicized above) are:
1. With contact tracing you keep all the data you collected. With exposure notification you throw away the data after notifying contacts.
2. With contact tracing you have to have proper security to store a bunch of private medical data. With exposure notification you don't.
3. With contact tracing you can identify asymptomatic carriers. With exposure notification, only the asymptomatic carriers have the information to identify themselves (assuming they keep all their exposure notifications).
4. With contact tracing, people don't have to assume they are an asymptomatic carrier, because the person doing the tracing will notify them if they are. With exposure notification, your only option is to assume you're an asymptomatic carrier for two weeks after every exposure, because no one person has enough information to identify asymptomatic carriers.
With contact tracing, you get contact data from person 2 and you keep that data. Then you get contact data from person 3, and you keep that data too, and by the time you get to person 4, you have fairly strong evidence that person 1 is an asymptomatic carrier and you can do that without quarantining anyone asymptomatic.
With exposure notification, you get contact data from person 2, and tell everyone they were in contact with, and then throw away that data. Then you get information from person 3 and you notify everyone they were in contact with, and then throw away that data too. As a researcher, even after person 8 you don't have any evidence that person 1 is an asymptomatic carrier (because you threw that evidence away at each step) and the best responsible asymptomatic people can do is assume they're asymptomatic carriers whenever they receive an exposure notification--they'll never actually know.
The key differences (which I italicized above) are:
1. With contact tracing you keep all the data you collected. With exposure notification you throw away the data after notifying contacts.
2. With contact tracing you have to have proper security to store a bunch of private medical data. With exposure notification you don't.
3. With contact tracing you can identify asymptomatic carriers. With exposure notification, only the asymptomatic carriers have the information to identify themselves (assuming they keep all their exposure notifications).
4. With contact tracing, people don't have to assume they are an asymptomatic carrier, because the person doing the tracing will notify them if they are. With exposure notification, your only option is to assume you're an asymptomatic carrier for two weeks after every exposure, because no one person has enough information to identify asymptomatic carriers.